Probably a dumb, simple question.
 

Low boost (3-4psi), shift, fluttering through intake filter. High boost (upwards of 12psi), shift, BOV sound through intake filter.

I had drove around with my hood off trying to get the car to recreate a metallic scraping noise I heard last night, and although it sounds nice I'm sure the BOV I have is not opening fast enough. Would this be an accurate assumption?

What would you recommend for a greddy rs replacement?

probably needs adjusting. it may be set to stiff and not blowing off at the low boost levels. google for adustment

Sounds normal to me.

This exact same issue happened to me at the beginning of this year, after the car sat for the winter. The BOV was fine, but it just needed to be lubed. It was dry af in there. Low boost wasn't enough to open the BOV, but high boost was. A little BOV lube on the piston and it fixed it!